Laser-assisted replication method

ABSTRACT

The invention concerns an apparatus and a process for producing a marking on a substrate. Substrates marked in that way are applied to documents such as for example credit cards, personal identity cards or banknotes as security features to provide protection from forgery. Embodiments of those security features have diffractive or holographic structures. The production of the markings was hitherto effected by shaping from a mold. A change in the marking is possible by changing the mole, which is time-consuming. The new apparatus and the new process are intended to permit the production of individualized markings on a substrate, at a low level of apparatus expenditure. 
     An embodiment of the apparatus according to the invention for producing a marking on a substrate, preferably a film, has a replication apparatus and a laser installation, which co-operates with the replication apparatus, by radiation from the laser installation being directed onto at least one irradiation region of the replication apparatus, for producing at least one shaping region. The apparatus further has a counterpressure apparatus, wherein a substrate is arranged between the replication apparatus and the counterpressure apparatus in order to shape the shaping region onto the substrate in a contact region between the replication apparatus and the substrate and wherein the feed of the radiation for producing the shaping regions extends outside the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application of InternationalApplication No. PCT/DE2003/002619 filed Aug. 5, 2003, which claimspriority based on German Patent Application No. 10236597.0, filed Aug.9, 2002, which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention concerns an apparatus for producing a marking on asubstrate, preferably a film, in particular a transfer film, comprisinga replication apparatus having a replication surface, and a device forproducing radiation, preferably a laser installation, which co-operateswith the replication apparatus, by the radiation being directed onto atleast one irradiation region of the replication apparatus for producingat least one shaping region, and a counterpressure apparatus, wherein asubstrate is arranged between the replication apparatus and thecounterpressure apparatus in order to shape the shaping region onto thesubstrate in a contact region between the replication apparatus and thesubstrate, and a process for producing a marking on a substrate,preferably a film, in particular a transfer film, wherein energy in theform of radiation, preferably laser radiation, from a device producingradiation is used for producing at least one shaping region on areplication surface of a replication apparatus, and wherein the shapingregion of the replication surface is shaped onto the substrate by thereplication apparatus contacting the substrate under pressure.

The protection of documents by security features has become a standardin the meantime, in the case for example of credit cards, personalidentity cards or banknotes. The forgery-proof character of thosefeatures is based on the fact that a high degree of special knowledgeand extensive apparatus equipment is necessary for the productionthereof. A particularly successful security feature which is difficultto copy is an OVD (optical variable device). Embodiments of thatsecurity feature have diffractive or holographic structures which, upona change in the angle of the incidence of light or the viewing angleduring visual checking of the authenticity of the security feature, leadto an optical effect such as for example a color change, a motif changeor a combination of the two. The security feature can thus be checked inrespect of its authenticity without further technical aids. An essentialcomponent part of those security elements is a generally thermoplasticor UV-hardenable layer into which the diffractive or holographicstructure is embossed in the form of a surface relief. That layer can bepart of a transfer film, in which case the security element is firstlyproduced and thereafter transferred onto the document to be safeguarded.That layer can also be produced in the form of an additional layerdirectly on the article to be safeguarded. The operation of transferringthe surface relief from a mold onto the thermoplastic layer is effectedby using rotating stamping cylinders as are described for example in EP0 419 773 or stamping punches as are disclosed for example in DE 2 555214. By virtue of the fine diffractive or holographic structuresproduction of the mold is technically very demanding and alsocost-intensive. For producing the molds firstly patterns, also referredto as masters, are produced for example by interfering laser beams andetching processes or by electron beam writing, and they are thengenerally galvanically shaped.

In the case of the known processes, for an enhanced forgery-proofnature, the endeavour is that the same security feature is not appliedto each document, but the security features are adapted to therespective document or the identity of the owner of the document, thatis to say they are individualized. In that respect two difficultiesarise with the above-mentioned processes:

On the one hand a large number of individualized masters would have tobe produced, which is very cost-intensive, and secondly the molds wouldhave to be respectively interchanged in the replication apparatuses, andthis would result in very long equipment preparation times.

As alternatives, processes and apparatuses are known which shape onlypartial regions of a mold in order to produce individualized securityfeatures.

CH 594 495 describes a process for stamping a relief pattern in athermoplastic information carrier, wherein selectively only partialregions of the mold are shaped into the thermoplastic layer. In terms ofprocess engineering, those shaping regions are selected by a procedurewhereby either those regions are heated by heating bands through whichcurrent flows or only selected shaping regions are pressed onto thesubstrate by a counterpressure device which has partial regions whichare adjustable in respect of height. A high level of local resolution inselection of the shaping regions is not to be expected with that processas heat conduction during the long heating-up and cooling-down phase forthe heating bands means that the boundaries of the shaping regions canbe only inaccurately defined or the dimensions of the shaping regionsare established by the dimensions of the bands or the dimensions of thepartial regions which are adjustable in respect of height. That processis consequently limited by virtue of having a low level of localresolution.

EP 0 169 326 describes an apparatus for producing a marking on asubstrate and the process corresponding thereto. The apparatus has areplication apparatus in the form of an unheated stamping mold and apressure plate which is in the form of a counterpressure apparatus. Thestamping mold has a replication surface which is structured withmicrostructures which are to be shaped. The apparatus has a laserarrangement for producing a laser beam which is directed onto thesubstrate through the counterpressure device. The known process providesthat firstly the substrate is pressed onto the pressure plate by thestamping punch. Absorption of the laser beam which is incident on thesubstrate directly in the stamping region and absorption of theradiation reflected at the replication surface of the stamping punchprovide that the substrate is selectively locally heated and raised to atemperature at which it can be permanently deformed. In that way shapingregions can be selected and transferred selectively by positioning ofthe laser beam. A limitation in that process and apparatus is that thelaser beam is guided through the substrate. That means that the processis limited to processing substrates which are transparent for the laserradiation and in addition it is highly sensitive to fluctuations in theabsorption properties of the substrate, which can occur for example dueto fluctuations in material, in dependence on the batch involved.

The object of the invention is to provide an apparatus and a processwhich permit the production of individualized markings on a substrate,preferably a film, at a low level of apparatus expenditure.

That object is attained by the apparatus set forth in claim 1 and theprocess set forth in claim 15.

SUMMARY OF THE INVENTION

The apparatus according to the invention serves for applying orproducing a marking on a substrate. The marking has a preferablydiffractively or holographically effective surface structuring or apreferably diffusely or directedly scattering matt structure which isapplied by means of replication processes to a thermoplastic layer of asubstrate, in particular of a body. The marking can be in the form of afigure, digit, character, surface pattern, surface image, text,numbering, security feature or of any other form.

The apparatus has a replication apparatus which can be of a rollernature or in the form of a stamping punch. The replication apparatus hasa replication surface which comes into contact with the substrate in acontact region in the co-operation of the replication apparatus and thesubstrate.

Shaping regions can be produced on the replication surface by means ofradiation which is applied to irradiation regions of the replicationapparatus, wherein surface structurings of the replication surface areshaped into the substrate in the shaping regions and the shaped surfacestructurings are formed in the substrate in such a way as to preferablypermanently remain therein.

The radiation is preferably produced by a laser installation but it isalso possible to use radiation which is not monochromatic or notcoherent.

The radiation preferably extends completely outside the substrate andimpinges on the replication apparatus in which it is partially orcompletely absorbed. The radiation path prior to impinging on thereplication apparatus is such that the substrate and the radiation pathdo not overlap. Prior to impingement on the replication apparatus theradiation is not transmitted through the substrate and in particular nosubstantial proportions of the radiation are absorbed in the substrate.In preferred embodiments the radiation, issuing from the laserinstallation, can be arranged parallel to the substrate and directedonto the replication apparatus so that the radiation passes outside thesubstrate.

With the apparatus according to the invention, partial regions of astamping mold can be selected targetedly by the radiation as desired forthe shaping operation and thus the markings formed from the shapingeffects on the partial regions can be of an individualized nature. It isparticularly advantageous in that respect that the process can becarried out by this apparatus independently of the absorption propertiesof the respective substrate as absorption of the radiation takes placesubstantially in the replication apparatus and not in the substrate. Itis further advantageous that the individualized identification istransferred in the form of the selection of the regions during the samereplication operation with a security feature, namely the for examplediffractive regions themselves.

An advantageous development of the invention provides that the apparatushas an additional energy source which is preferably separate from theradiation-producing device. The additional energy source which can be inthe form of a controllable heat source provides for temperature controlof the replication apparatus in the region of the replication surface,preferably homogenously for a relatively large portion of thereplication surface. It is in thermal contact with the replicationapparatus or energy can be contact-lessly transmitted to the replicationapparatus by radiation. In addition, in advantageous configurations, theadditional energy source is separate from the radiation-producingdevice. The additional energy source can introduce the energy into thereplication apparatus independently in respect of time and location fromthe energy input from the radiation-producing device. In preferredembodiments the input of energy from the additional energy source ispreferably permanently effected into the replication apparatus at a timeprior to the input of energy from the radiation-producing device orlocally in relation to the direction of movement of the replicationsurface prior to the input of energy from the radiation-producingdevice. The input of energy into the replication apparatus by theadditional energy source preferably requires no or only a low level oflocal resolution, while in addition the local distribution of the energyinput does not have to be rapidly variable. The additional energy sourcecan be of a structurally simpler and less expensive nature by virtue ofthose lower demands, in contrast to the radiation-producing device.

Zones at different temperatures can be produced on the replicationsurface by the co-operation of the temperature field of the replicationsurface, which is produced by the additional energy source, with thelatent heat image produced by the radiation. Only the zones of thereplication surface whose temperatures are within the process window ofthe shaping operation are durably permanently shaped into the substrate.

The additional energy source can act on the entire surface area or onsurface portions of the replication surface. In embodiments in which theadditional energy source acts substantially or over the full surfacearea preferably homogenously with a temperature-setting action on thereplication surface, the shaping regions can be decisively determined bythe radiation, for example the laser radiation. In other constructionsonly partial regions of the replication surface are in particularhomogenously subjected to temperature control, in which case by virtueof that process implementation the shaping regions are then preferablyrestricted to the temperature-controlled regions. In those embodimentsan initial preliminary selection of the shaping regions is effected byvirtue of the selection of the partial regions on which the additionalenergy source acts.

The additional energy source can be permanently or temporarily connectedto the replication apparatus by way of direct thermal contact, forexample in the form of heating wires or strips or inductive heatingdevices which are completely or partially integrated in the replicationapparatus. Energy transfer in other embodiments can be effected bycoherent or incoherent radiation, in particular laser radiation, orconvection, in which case the additional energy source is for example inthe form of a heating laser device or a heat radiating device.

An advantageous configuration provides that there is a control means, inparticular a freely programmable control means, which controls theselection of the irradiation regions preferably by actuation of theradiation-producing device.

In this advantageous development the patterns of the markings areprepared in the form of preferably digital items of information, forexample as a data file, which were produced by image processingprograms, by computer-aided processes or the like. Those items ofinformation are converted by the control means, in particular byactuation of the laser installation, into a time-dependent change in thepower density in relation to surface area of the radiation impinging onthe replication apparatus. The change in the power density in relationto surface area is preferably effected by a sequentially writing laserbeam or by a change in the beam profile by means of a controllableimaging mask. The shaping regions and thus the pattern of the markingare determined by the controlled selection of the irradiation regions.

Particularly if the replication apparatus is embodied in the form of areplication roller, it is possible to produce extended markings withpatterns, wherein the patterns can be longer in the direction of advanceof the substrate, than the periphery of the replication roller. It isalso possible to produce patterns whose longitudinal extent in thedirection of advance of the substrate is a multiple of the transverseextent thereof, for example a banner in the transverse format with textor wallpaper. In particular the pattern can have an endless design, thatis to say a configuration in which component parts of the pattern arenot repeated or are repeated independently of the roller periphery.

A further development of the apparatus is advantageously provided ifthere is a cooling apparatus for cooling the replication surface, bywhich in particular a latent heat image produced can be extinguished ormodified in some way. The cooling apparatus can be in the form of ablower, in which case an air flow produced by the blower is directedonto the replication surface and cools same. A gas flow cooling actioncan perform a similar function, in which case a flow of gas, preferablya flow of nitrogen or inert gas, impinges on and also cools thereplication surface.

In further configurations, the cooling apparatus can be in the form of acooling roller which is arranged in parallel displaced relationship withrespect to the replication roller and contacts same along a line-shapedsurface. The thermal contact between the replication roller and thecooling roller provides for dissipation of heat and thus cooling of thereplication roller.

When using a replication roller the cooling apparatus is preferablyarranged in such a way that it acts on the replication surface in aregion which, in the direction of rotation of the replication roller, isbetween the contact region of the replication apparatus and thesubstrate and the point of impingement of the radiation on thereplication surface.

A further advantageous development of the apparatus provides that thereplication surface is structured with a surface relief. That surfacerelief is the negative for the structures which are transferred onto thesubstrate in the shaping operation. The replication surface can becompletely or partially structured. The depth of the surface relief ispreferably between about 0 and 20 μm, in particular between 0.1 and 0.5μm. Particularly for forming a diffractive or holographic structure onthe substrate, the surface relief can be produced in a gratingconfiguration in partial regions or over the full surface area involved.The grating spacing, that is to say the spatial frequency, is preferablybetween 4,000 lines per mm and 10 lines per mm, in particular 1,000lines per mm. The replication surface can also be subdivided intopartial regions whose dimensions are preferably less than 0.3 mm andwhich differ from each other by virtue of the spatial frequency, thegrating orientation, the grating nature or other parameters.

In a further advantageous configuration of the invention the partialregions can be arranged in periodically repetitive manner, in particularalternatingly. Possible embodiments provide that a respectivearrangement of various partial regions, that is to say for example anarrangement of between two and six and preferably three partial regions,forms a pixel unit. A plurality of pixel units can be arranged to form asurface image. Preferably the three partial regions referred to by wayof example, by virtue of their grating structure, represent the threeprimary colors. That pixel unit or also the partial regions can bearranged on the replication surface in regularly or periodicallyrepetitive relationship, for example in grating form or alternatingly.

In particular to produce a matt structure on the substrate the surfacerelief can also be provided with surface structures which involve astochastic or quasi-stochastic distribution. A matt structure on asubstrate produces a particular optical effect in the form of diffusescatter of the light incident on the substrate. For producing a mattstructure, the surface relief has surface structures, for examplegrooves, channels, craters, holes etc., of which the respective shapesand/or orientations are similar or of any desired nature and which canbe distributed on the replication surface uniformly, stochastically orquasi-stochastically. For example the surface relief can be providedwith a structure similar to a brushed surface.

In a further advantageous configuration the replication apparatus has apressure die or mold of metal film, in particular nickel or a nickelcompound. The use of metal films of nickel or nickel compoundsfacilitates galvanic shaping of a diffractive structure for producing amaster. As an alternative to those materials it is also possible to usea material which has a particularly high level of absorption and inparticular a higher level of absorption than nickel, for the wavelengthof the laser radiation used. That provides that the energy required forproducing the latent heat image on the replication apparatus, preferablyon the replication surface, would be markedly reduced. Accordinglylower-power and thus less expensive lasers could be used in theapparatus.

The laser installation can be desirably have a scanner system and/or amask projection system. For using a scanner system, the laser beam isshaped in such a way that the diameter of the laser spot upon impingingon the replication apparatus is preferably in a range of between 0.05 mmand 2.0 mm. That laser spot can be guided in sequentially writing modeover the replication apparatus by the scanner system. In that case thescanner system can be a system with deflection devices, for exampledeflection mirrors, or a system with flying optics. The position of thelaser spot on the replication apparatus can be altered by the user by acontrol means, preferably a path control means, so that variousgeometrical shapes, images, letters and numbers can be flexibly writtenon the replication apparatus with the laser spot. In other embodimentsthe replication apparatus can be exposed over its surface by a maskprojection system. In that case the beam shaping system can be such thatthe image of a mask, for example by a 4f-structure, is produced on thereplication apparatus in such a way that the shape of the laser spotcorresponds to the shape of the openings in the mask. In that case themask can be a rigid mask or however a matrix arrangement of elementswhich controlledly transmit or extinguish the laser beam, which elementscan be for example movable mirrors or liquid crystal elements.

In addition the apparatus can be of such a design configuration that thelaser beam produced by the laser installation is controllable orregulatable in respect of further parameters such as power and/or powerdensity in relation to surface area and/or distribution of power densityin relation to surface area. The total energy input in the replicationapparatus is determined by the power and the switch-on duration (beam-ontime) of the laser. The time-dependent power density in relation tosurface area on the replication surface together with the switch-onduration of the laser determines the energy input per unit of surfacearea into the replication apparatus.

Semiconductor, sold state or gas lasers, in particular Nd:YAG, excimeror diode lasers, can be used in the laser installation. Diode lasers asrepresentatives of semiconductor lasers enjoy advantages as they can bequickly modulated in power and are convenient and desirable in terms ofacquisition. The laser radiation from a diode laser array can be focusedby way of a common optical system onto the replication apparatus,providing a common focus, or the diode laser array produces an imageover a surface area, in which case switching individual diodes orregions of the diode laser array on or off makes it possible toimplement areal exposure of the replication apparatus with acontrollable level of power density in relation to surface area ordistribution of the power density in relation to surface area. In otherembodiments the laser beam is passed by way of one or more, inparticular also image-transmitting optical waveguides.

An advantageous configuration of the apparatus is provided if the laserbeam is directed onto the replication surface of the replicationapparatus, impinging on the replication surface. In this embodiment thelaser beam is directed onto the replication surface of the replicationapparatus by the beam guidance and shaping effect, so that it is atleast partially absorbed in the replication apparatus in the region ofthe replication surface, and introduces an energy input into thereplication surface. In embodiments of the replication apparatus in theform of a rotating cylinder, the location of laser exposure ispreferably in front of the replication gap on the cylinder in thedirection of rotation thereof, the replication gap being the contactregion between the replication apparatus and the substrate. The spacingbetween the point of impingement on the cylinder and the replication gapcan be such that the latent heat image produced still does not becomeblurred by virtue of thermal conduction, and the replication apparatusis still not covered by the substrate. The interaction of the laser beamwith the replication apparatus in this embodiment takes place on thereplication surface. This embodiment has the advantage that the processof temperature field production and thus selection of the shapingregions is dependent on the material of the mold and independent of thematerial properties, in particular absorption or transparency, of thesubstrate used.

A further advantageous configuration of the apparatus is provided if thereplication apparatus has an inside surface which is parallel to and/orconcentric with the replication surface and the radiation is directedonto the inside surface so that the laser beam impinges on the insidesurface. The laser beam is not directed onto the replication surface oris not directed only thereonto, but it can impinge on a surface which isarranged on the rear side of the replication surface. That secondsurface can be in thermally conductive contact with the replicationsurface, in which case in particular the resistance to heat conductionis such that it is similar or the same over the entire surface area orin partial regions. If now that second surface is subjected to the laserradiation and heated, the replication surface is also heated by virtueof heat conduction. For exposure of the second surface to the radiation,it can be provided in terms of apparatus that the laser beam is directedin the opposite direction to the surface normal to the second surfaceand impinges on that inside surface. In this embodiment of thereplication apparatus in the form of a rotating cylinder, the locationof exposure can be in a region which in the direction of rotation beginsupstream of the replication gap and terminates in the replication gap,in which respect the term replication gap is used to denote the contactregion between the substrate and the cylinder during the shapingoperation. The position of laser irradiation can also be dependent onspeed of rotation, laser power and thermal resistance between the secondsurface and the replication surface.

An advantageous development of the replication apparatus provides thatvarious layers are arranged between the inside second surface and thereplication surface. As already mentioned, the outermost layer isgenerally formed from a metal film, in particular a film of nickel or anickel compound. A heat-conducting layer and/or an absorption layer canbe disposed on the side of said layer which is remote from thereplication surface, in which case the absorption layer has a differentlevel of absorption from the metal film and in particular a higher levelof absorption. In addition it is possible to arrange a transparent layerwhich can also be a body which is transparent in relation to the laserwavelength, in particular a plate or a cylinder casing.

The object of the invention is further attained by a process as setforth in claim 15. The process provides for the production of a markingon a substrate, preferably a film, in particular a transfer film,wherein energy in the form of radiation, preferably laser radiation, isused by a radiation-producing device for producing at least one shapingregion on a replication surface of a replication apparatus, and whereinthe shaping region of the replication surface is shaped onto thesubstrate by the replication apparatus contacting the substrate underpressure, and wherein the radiation for producing the shaping regions issupplied completely outside the substrate.

The replication apparatus is exposed with radiation, in which case theradiation can act directly on the replication surface of the mold andheats the mold or it can be absorbed by other regions of the replicationapparatus and heats the mold, in particular the replication surface ofthe mold, by thermal conduction.

By virtue of irradiation of selected regions of the replicationapparatus, regions at different temperatures can be produced on thereplication surface of the mold. In particular regions are produced at atemperature which corresponds to the working temperature of the shapingoperation, these being referred to as shaping regions.

In that case the radiation is guided in such a way that it does notpenetrate into the substrate before impinging on the replicationapparatus.

In the co-operation of the substrate and the replication apparatus underpressure the shaping regions of the mold which are produced can bedurably permanently shaped into a substrate.

The individualized marking preferably comprises the shapings of thepartial regions of the replication surface, which were selected by theabove-described temperature implementation process for a shapingoperation. Individualization of the markings, that is to say the changein the selection of the regions shaped, can thus be effected by a changein the temperature distribution on the replication surface. A change ofthat nature can be effected by way of control of the radiation-producingdevice, for example the laser installation, or the corresponding beamguidance and shaping devices.

In preferred developments of the process the replication apparatus issubjected to a temperature control effect at least in partial regions ofthe replication surface, using an additional energy source. The latteris preferably provided separately from the radiation-producing device.

In this embodiment of the process, in a process step the replicationapparatus can be heated with the additional energy source so thatregions or at least partial regions of the structured replicationsurface of the mold are at a first temperature. In that respect theenergy input is in particular to be such that the heated regions orpartial regions of the replication surface which do not contain anyadditional energy input by the radiation are at the first temperatureduring the shaping operation.

In a further step in the process the replication apparatus is exposedwith radiation.

The co-operation of heating of the replication apparatus by theadditional energy source and selective heating by the radiation resultsin the production on the replication surface of the mold of regionsinvolving different temperatures, in particular at least two regionswhich are temperature-controlled in different ways. A part of theregions preferably involves the first temperature while another part ofthe regions preferably involves a second temperature which is achievedby the additional energy input by virtue of the radiation. By virtue ofthe way in which they are produced, the regions involving the secondtemperature can be referred to as heat combination regions.

The process can be carried out in such a way that either the firsttemperature or the second temperature corresponds to the workingtemperature of the shaping operation so that, in a further step in theprocess, either the partial regions at the first temperature or thepartial regions at the second temperature can be durably permanentlyshaped onto the substrate.

There can be a time interval between the energy input by the additionalenergy source or the radiation-producing device and the shapingoperation, by virtue of the period of time required for the movement ofthe partial region from the position of the energy input to the positionof the shaping operation. If there is a time interval between heating ofa partial region of the replication surface and the shaping operation inrespect of that partial region, then the heat field distribution whichis initially produced on the replication surface can alter due to heatconduction effects. In particular the set temperatures in the heatedregions can decrease as heat can flow away for example into thereplication apparatus. For possible compensation for that effect,regions or partial regions of the replication surface can firstly be setto a higher temperature than in particular the first or secondtemperature respectively so that, after the heat losses due to heatconduction, during the subsequent shaping operation, those regions orpartial regions are then at the first and second temperaturerespectively.

It is advantageous if that time interval is as short as possible or ifthat time interval is at least equal for all partial regions of thereplication surface as then the heat conduction effects are of asimilarly pronounced degree, in regard to all partial regions.

The process can also be operated continuously, in which respect processsteps are carried out at the same time.

The process can be implemented in such a way that the first temperatureis in a plastic temperature range for the respective substrate and thesecond temperature is in a flow temperature range.

If the replication apparatus is in contact with the substrate underpressure and while there is in a partial region a temperature which isin the plastic temperature range, the structured replication surface isdurably permanently plastically shaped in that partial region.

If the temperature is within a flow temperature range which is above theplastic temperature range, then after separation of the mold from thesubstrate, the deformed material of the substrate will begin to flow. Asa result, the shaped surface structurings of the substrate material aresmoothed so that they are not retained as optically active structures onthe substrate.

In this implementation of the process therefore the partial regionswhich have been raised to plastic temperature and which have notreceived any additional heat input by virtue of the radiation can betransferred onto the substrate. Negative selection of partial regionscan be effected by virtue of the radiation.

In accordance with another configuration of the process the firsttemperature is set in an elastic temperature range and the secondtemperature in a plastic temperature range, the elastic temperaturerange being below the plastic temperature range.

When a shaping operation is carried out, the partial regions whosetemperature is in the elastic temperature range will cause only elasticdeformation of the substrate. After separation of the mold from thesubstrate the surface structures produced experience elastic return andthe substrate again assumes approximately its original surface shape.

In this embodiment of the process therefore the heat combination regionsare selectively transferred. The additional heat input by the radiationtherefore represents positive selection of partial regions.

The substrate can be made up of a plurality of layers. The specifiedtemperatures or the specified temperature ranges of the substrateinvolve in particular temperatures or temperature ranges of athermoplastic layer which is component part of the substrate. Furtherlayers of the substrate, for example the carrier layer of the substrate,can be at a different temperature. In general terms the temperature orthe temperature range of the substrate is preferably the temperature orthe temperature range of the thermoplastic layer.

In an advantageous development of the process the replication surface,prior to the interaction with the radiation, is heated completely oronly in partial regions, in a homogenous manner. The heating of surfaceportions means that a coarse selection of the partial regions to betransferred can already be effected in the initial stages as it ispossible that partial regions, without that heating, do not reach theworking temperature necessary for the shaping operation.

In a further advantageous modification the replication surface is cooledcompletely or in partial regions after the shaping operation and priorto the following energy input by the radiation-producing device. Coolingcan be effected by heat dissipation by way of a thermal contact and/orair or gas cooling. The cooling operation, particularly in permanentoperation of the apparatus, provides that the temperature field of thereplication surface is controlledly reduced to temperatures which arepreferably below the necessary temperature for a shaping operation. Inaddition cooling obviates overheating of the replication apparatus.

In further embodiments the radiation is either directed directly ontothe replication surface or the radiation is applied to a surface remotefrom the replication surface. When the replication surface is subjectedto exposure, the angle of incidence of the laser radiation can bevaried, in particular if the replication apparatus is in the form of aroller-like stamping cylinder. Changes in the angle of incidence of thelaser radiation on the replication surface can lead to marked changes inabsorption of the laser radiation. Thus the angle of incidence can beused as an additional process parameter to be varied in carrying out theprocess.

It is advantageous in regard to applying the radiation to a surfaceremote from the replication surface, that the irradiation operation canbe effected shortly before the mold comes into contact with thesubstrate or while the mold is already in contact with the substrate.The surface remote from the replication surface can be of such a naturethat it is accessible for the radiation when the mold is already incontact with the substrate. The time interval between irradiation andthe shaping operation can thereby be freely adjusted.

An advantageous development of the process provides that the replicationapparatus used is a replication roller, wherein application of theradiation to the replication roller takes place at a first angularposition of the replication roller and contact of the replication rollerwith the substrate takes place at a second angular position. Optionally,cooling of the replication roller takes place at a third angularposition and a temperature control effect for the replication rollertakes place at a fourth angular position. The process is of anadvantageous configuration if the intermediate angle between the firstand second angular positions in the direction of rotation of thereplication roller is so small that the latent heat image produced bythe radiation in the first angular position, after rotation of thereplication roller into the second angular position, still has sharpcontours. That is afforded for example if the lack of sharpness or blurof the latent heat image, which has occurred due to heat conduction, isless than the reciprocal, desired resolution of the replication process.The definition of the blur circle from geometrical optics can be used asa measurement in respect of lack of sharpness. The angle between thesecond and first angular positions in the direction of rotation ispreferably to be set at as large a value as possible, in particulargreater than 180°, in order to achieve homogenization of the temperatureprofile on the replication surface. The angles between the second andthird angular positions and/or between the third and fourth angularpositions are each preferably to be set at as small a value as possible,in particular less than 90°, in the direction of rotation, in order alsoto promote homogenization of the temperature profile on the replicationsurface.

In preferred embodiments the radiation is transmitted to the replicationapparatus either over an area and/or in point fashion in sequentiallywriting mode. In particular advantages are afforded if the writingprocess is used together with a rotating stamping cylinder and thereplication surface is exposed to radiation. In this embodiment, due tothe apparatus structure involved, there is a time interval between theoperation of heating a partial region of the replication surface and theshaping operation in respect of that partial region, as the replicationsurface is covered by the substrate during the shaping operation andcannot be exposed to radiation. If the information is transferred ontothe mold in line-wise writing mode by the radiation and if that line isarranged parallel to the replication gap, that at least ensures that thetime interval between the exposure process step and the shaping processstep is approximately equal for any exposed point on the mold.

Corresponding advantages are afforded with the combination of arealexposure and the use of a stamping punch. In this case an equal timeinterval between heating and shaping of the partial regions is achievedif initially all partial regions are simultaneously exposed to radiationand then all partial regions are simultaneously shaped. It is howeveralso possible to use the combinations of a writing process and stampingpunch, and areal exposure and a stamping cylinder, if that affords otheradvantages, for example advantages in the radiation exposure process.

This apparatus and process consequently make it possible to shapevarious markings, for example including document-specific orperson-specific markings, onto a substrate from a single mold, in whichrespect partial regions of that mold can be selectively activated ordeactivated for the shaping operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, details and advantages of the invention will beapparent from the description hereinafter of an embodiment by way ofexample of the process and embodiments by way of example of apparatusesfor producing a marking. In the drawing:

FIGS. 1 a, b and c show embodiments of an apparatus for applying amarking to a substrate,

FIG. 2 a shows a detail sectional view in a section planeperpendicularly to the substrate through the line II-II of theembodiment in FIG. 1 a with a first implementation of the process,

FIG. 2 b shows a diagrammatic view of the relationships between heatdistribution on the replication apparatus and the shaped region on thesubstrate in accordance with the process illustrated in FIG. 2 a,

FIG. 3 a shows a detail sectional view in a section planeperpendicularly to the substrate through the line II-II of theembodiment in FIG. 1 a with a second implementation of the process,

FIG. 3 b shows a diagrammatic view of the relationships between heatdistribution on the replication apparatus and the shaped region on thesubstrate in accordance with the process illustrated in FIG. 3 a,

FIG. 4 shows a diagrammatic view of the heat distribution in a portionof a replication apparatus in cross-section upon exposure with a laserbeam,

FIGS. 5 a and b show diagrammatic views illustrating the principle forthe production of a negative and positive image respectively,

FIG. 6 shows a plan view of a portion of the surface of the replicationapparatus of FIG. 1 a and a marking which was produced by thereplication apparatus, and

FIG. 7 shows a detail sectional view in a section plane perpendicularlyto the substrate through the line II-II of the apparatus in FIG. 1 a ofa modified embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 a is a diagrammatic view showing the structure of an embodimentof an apparatus for producing a marking on a substrate 43. In theillustrated embodiment the substrate 43 is in the form of film. The filmcan be a transfer film. The apparatus has a replication roller 41 and acounterpressure apparatus 42 in the form of a roller, the substrate 43being guided between the replication roller 41 and the counterpressureapparatus 42. The replication roller is exposed from the outside with alaser beam 30.

The substrate 43 is of a thickness of less than 1 mm and can be in theform of a multi-layer composite. At least one layer comprises atransparent plastic material. Further layers can be in the form ofmetalization layers, interference layers, protective layers, carriermaterial layers or adhesive layers.

The preferably metallic or metallically encased replication roller 41 isprovided with surface structurings in the form of diffraction stampingstructures 46 on its replication surface. The diffraction stampingstructures 46 are of a depth of between about 0 and 20 μm and involveline spacings or spatial frequencies of between 10 lines per millimeterand 4,000 lines per millimeter.

The counterpressure apparatus 42 is in the form of a cylindrical rollerand can comprise rubber or can have a casing consisting of rubber.

The arrow 48 and the arrow 49 show the respective directions of rotationof the replication roller 41 and the counterpressure apparatus 42, thereplication roller 41 rotating in the clockwise direction and thecounterpressure apparatus 42 rotating in the counter-clockwisedirection. The arrow 47 points in the direction of advance of thesubstrate 43 which moves towards the left in FIG. 1 a. The replicationroller 41, the substrate 43 and the counterpressure apparatus co-operatein such a way that the replication surface with the diffraction stampingstructures 46 is pressed under a given, generally adjustable pressureagainst the substrate 43 during the rotation of the replication roller41 and the counterpressure apparatus 42. Shaping of the surface 44 inthe form of a marking 45 on the substrate 43 takes place in the contactregion between the replication roller 41 and the substrate 43.

The laser beam 30 can expose the surface 44 in areal manner or inmodified embodiments in punctiform sequential fashion. Actuation of thelaser beam 30 in respect of power, beam direction, power density inrelation to surface area and so forth is effected by a control device.The laser beam 30 can be pulsed or power-modulated, it preferablyoperates at constant power. The laser beam 30 can be stationary or movedin the exposure operation. In the case of areal exposure, for example bymeans of a mask projection process, the laser beam is preferablystationary while the replication roller rotates. In modified embodimentsthe movement of the laser beam 30 takes place synchronously with respectto the rotating replication roller 41, in the direction of the arrow 90.In the case of writing exposure processes using a punctiform or almostpunctiform laser beam 30, the movement of the laser beam 30 can besynchronous with respect to the rotating replication roller 41 in thedirection of the arrow 90 and also parallel to the longitudinal extentof the axis of rotation of the replication roller 41 in the direction ofthe arrow 91. For punctiform exposure, the laser beam can be focused andcan involve a small beam diameter, for example less than 1 mm.

The replication roller 41 is heated by a controllable heat source (notshown) which is an inner heat source, that is to say which acts at theinterior, so that the entire region of the replication surface which hasthe diffraction stamping structures 46 is at a preferably unitarytemperature which is below the shaping temperature of the substrate 43,that is to say below the plastic temperature range in the elastictemperature range of the substrate 43.

Only the partial regions of the replication roller 41 are shaped,producing a durably remaining marking 45, if those partial regions, inaddition to heating with the inner heat source, have been exposed withthe laser beam 30, constituting a heat combination region. An additionalenergy input takes place within the irradiated surface 44 by the laserbeam 30 which can be directed onto the replication roller 41 at anyangle, thus resulting in a latent heat image, shown in FIG. 1 a in theform of a rectangular area 44, on the replication roller 41. The latentheat image can be of a simple geometrical shape such as for example acircle, a multi-angled shape, a closed polygon, but also the shape ofletters, digits or symbols. Energy input into the surface 44 by means ofthe laser beam 30 is effected on the rotating replication roller 41 in aregion which is at a spacing of an angle of rotation of about 90° fromthe region in which the shaping operation is carried out. That spatialspacing results in a time interval between irradiation and shaping. Theenergy input by the laser beam 30 is such that, within the irradiatedsurface 44, the temperature after the exposure operation is within theplastic temperature range of the substrate 43 or, in order to compensatefor thermal conduction effects by virtue of the time interval involved,above the plastic temperature range of the substrate 43. By virtue ofthat temperature control procedure the partial region 44 of thereplication roller 41 is at a surface temperature, in the replicationoperation, which is in within the plastic temperature range, and thesubstrate 43 is durably permanently shaped in the contact region betweenthe replication apparatus 41 and the substrate 43. Any shape andstructure of the marking 45 can be produced on the substrate 43 byaltering the shape and structure of the irradiated surface 44.

In a possible mode of operation of the apparatus the laser beam 30 isswitched on and off in control sequences, thus preferably producingmarkings 45 which are offset from each other and in particular spatiallyseparated. The configuration of those various markings 45 can be thesame in each case or can differ from one marking to another by virtue ofindividualized features, for example by serial numbering.

In a further possible mode of operation of the apparatus in FIG. 1 a thelaser beam 30 can be continuously switched on and the impingement pointof the laser beam 30 on the replication roller 41 is moved synchronouslywith respect to the replication roller 41 in the direction of the arrow90 and in the transverse direction with respect thereto in the directionindicated by the arrow 91, for example by parallel displacement or byangular deflection of the laser beam 30. In that mode of operation amarking 45 can be formed, with a pattern which varies in the directionof advance 47 of the substrate 43.

In particular this mode of operation allow control sequences ofmovements of the laser beam 30 for producing an individual marking to beimplemented over a plurality of revolutions of the replication roller41, that is to say over a plurality of working cycles.

For example it is possible in that way to produce text of any length inthe direction of advance movement 47, on the substrate.

In a modification of that mode of operation the laser beam 30 iscontinuously switched on and the change in the power density in relationto surface area on the replication roller 41 is effected by a change inthe beam profile of the laser beam 30.

A combination of those modes of operation is also possible.

FIG. 1 b shows a modified embodiment of the apparatus in FIG. 1 a,involving an areal exposure process. The apparatus in FIG. 1 b issimilar to the apparatus in FIG. 1 a, but the apparatus in FIG. 1 b hasa diode laser array 93 as the radiation-producing apparatus.

The diode laser array 93 includes a plurality of diode lasers 94 whichare respectively arranged in parallel relationship with each other andin the same orientation in an array so that the radiation emissiondirection is the same in the case of all diode lasers 94. The diodelasers 94 are individually actuable and modulatable in their power, byway of a control device (not shown). The diode laser array 94 isarranged with its longitudinal extent parallel to the longitudinalextent of the axis of rotation of the replication roller 41, the laserbeams 30 thus being directed onto the replication roller 41. The spacingbetween the diode laser array 93 and the replication roller 41 isdependent on the radiation characteristic of the diode lasers 94, ordependent on an optional interposed optical arrangement (not shown inFIG. 1 b), and is of such a nature that it produces a power densitydistribution of the laser beams 30 on the replication roller 41, whichcorresponds to the requirements involved. By virtue of a combination ofvariations in power density in relation to surface area, which arecaused by the controlled modulation of the diode lasers 94, and therotational movement of the replication roller 41, it is possible toproduce any exposure patterns in the replication roller 41, by means ofwhich any markings 45 can be produced on the substrate 43.

FIG. 1 c shows a further modified embodiment of the apparatus of FIG. 1a with a writing exposure process. The apparatus of FIG. 1 c has anarrangement in which, similarly to the arrangement of FIG. 1 a, asubstrate 43 is guided between a replication roller 41 and acounterpressure apparatus 42 and a marking 45 is produced thereon. Thereplication roller 41 is also exposed with radiation from the outsidewith a laser beam 30. The laser beam 30 is passed from a laser source94, with the interposition of an optical arrangement 95 and a deflectionunit 96, onto the replication roller 41 where the laser beam impingesthereon, producing an impingement point 101. The laser source 94 isdiagrammatically shown as a cuboid in FIG. 1 b and can be of any desiredconfiguration, for example in the form of an Nd:YAG, excimer, solidstate, gas, semiconductor laser and so forth. The laser source 94 isarranged above the substrate 43 and spaced from the replication roller41, being oriented in such a way that the laser radiation 30 issuing atthe output is arranged in approximately parallel displaced relationshipwith respect to the longitudinal extent of the axis of rotation of thereplication roller 41. In further configurations of the apparatus thelaser source 94 can also be so arranged that the laser radiation 30issuing therefrom is arranged approximately perpendicularly to thesubstrate 43 and is suitably diverted. The optical arrangement 95 isarranged downstream of the laser source 94 in the direction ofpropagation of the laser beam 30 and has optical components for beamguidance and shaping.

In the deflection unit 96 which is arranged at a downstream position inthe direction of propagation of the laser beam 30, the laser beam 30 isdeflected through a controllable angle alpha, so that the impingementpoint 101 can be guided over the replication roller 41 in movementsparallel to the longitudinal extent of the axis of rotation of thereplication roller 41.

The deflection unit 96 has a drive unit 98, for example a motor, inparticular a servomotor or a stepping motor, or a galvanometer drive,and a mirror 97 which is connected by way of a drive shaft 99 and has areflecting front side. The drive shaft 99 is driven by the drive unit 98and is rigidly connected to the mirror 97. The drive shaft 99 and themirror 97 can be arranged relative to each other in such a way that theaxis of rotation of the drive shaft 99 is in the plane of the reflectingfront side of the mirror 97 and the drive shaft 99 does not or onlyslightly masks the reflecting front side of the mirror 97. In thatarrangement a rotary movement of the drive shaft 99, which is producedby the drive unit 98, can cause the reflecting front side of the mirror97 to be rotated about an angle, with the formation of an axis ofrotation in that situation.

The deflection unit 96 is so arranged that the laser beam 30 meets thereflecting front side of the mirror 97 at an angle of alpha/2 and thetilt axis of the reflecting front side of the mirror 97 is arrangedapproximately perpendicularly to a plane which is formed by the laserbeam 30 which is incident on and is reflected by the deflection unit 96.

The optical arrangement 95 can also be arranged downstream of thedeflection device 96.

The position of the impingement point 101 on the replication roller 41in parallel relationship with the longitudinal extent of the axis ofrotation of the replication roller 41 is controlled by the deflectionunit 96. In combination with the rotational movement of the replicationroller 41, an exposure pattern 100 is produced on the replicationroller. In the view in FIG. 1 c the exposure pattern 100 is in the formof a heat path which is written line-wise and which is sequentiallyexposed, in the form of a line extending continuously. The heat pathextends almost parallel to the axis of rotation of the replicationroller 41, the direction of advance of the impingement point 101changing at each line change.

FIG. 2 a shows a sectional view of the apparatus of FIG. 1 a. Thesubstrate 43 has a layer structure comprising a thermoplastic layer 51,a second layer 52 and a carrier film 50 which is for example polyesteror polycarbonate film. The second layer 52 and further layers is or areoptional. The second layer 52 or further preferably different layers arein the form of a protective lacquer layer, a metalization layer, aninterference layer or an adhesive layer.

The replication roller 41 has diffraction stamping structures 46 whicheither, as diagrammatically shown here, can be applied over the entireperiphery preferably over the full area involved, or however can also beapplied only in partial regions.

As already mentioned above, in the rolling operation in respect of thereplication roller 41, the replication roller 41 and the substrate 43co-operate under pressure, in which case the replication roller 41rotates in the direction of rotation indicated by the arrow 48 and thesubstrate 43 moves in relation thereto in slip-free relationship in thedirection indicated by the arrow 47. The replication roller 41 is heatedentirely or in partial regions by the controllable inner heat source(not shown). The laser beam 30 is directed onto the replication roller41 from the exterior and in a region upstream of the replication gap 53,impinges on the replication surface of the replication roller 41, thatsurface carrying the diffraction stamping structures 46; the termreplication gap 53 is used to denote the contact region between thereplication roller and the substrate in the shaping operation.

In the embodiment of the process which is shown in FIG. 2 a thereplication surface is raised by the inner controllable heat source to atemperature which is within the elastic temperature range. Theadditional energy input by the laser beam 30 provides that theirradiated surfaces 70 are further heated and thus represent the heatcombination regions. The energy inputs are such that the replicationsurface of the replication roller 41, upon making contact with thesubstrate 43 in the regions 70, is at a temperature which is within theplastic temperature of the substrate 43 and that the remaining regionsare at temperatures which are below the plastic temperature range andfor example in the elastic temperature range of the substrate 43. In theoperation of shaping the diffraction stamping structure 46 onto thesubstrate 43, with that temperature distribution, only the regions 70are durably permanently shaped into the thermoplastic layer 51. In thatway a marking 45 whose surface portions which are shaped into thesubstrate 43 have diffractive structures are introduced into a substrate43, as an individualized security feature.

The principle of positive selection or negative selection of partialregions on the replication surface of the replication apparatus forshaping onto a substrate will now be described in greater detail withreference to the graphs in FIG. 2 b.

FIG. 2 b shows a co-ordinate system 20, wherein the portion of theperiphery of a stamping roller is plotted on the horizontal X-axis whilethe temperature on the replication surface of that stamping roller isplotted on the vertical Y-axis, at the respective position along theperiphery of the roller.

The temperature scale can be qualitatively subdivided into three ranges:the first range is the elastic temperature range T_(elast). Thetemperature range disposed thereabove, involving higher temperatures, isthe plastic temperature range T_(plast). The highest temperature rangeshown here is the flow temperature range indicated at T_(fliess).

It is only in the plastic temperature range T_(plast) that thestructured surface of the roller is durably permanently shaped onto thesubstrate. That range therefore represents the process window for asuccessful shaping operation.

The elastic temperature range T_(elast) is established at lowertemperatures. Admittedly, elastic deformation of the substrate takesplace here upon contact occurring between the stamping roller and thesubstrate, which takes place under pressure, at least at temperaturesnear to T_(plast), but as soon as the stamping roller and the substrateare separated again the substrate returns to its original generallysmooth surface configuration with an elastically resilient or dampedmotion.

In the flow temperature range T_(fliess), initially deformation takesplace when contact is made between the stamping roller and the substrateunder pressure. When however the stamping roller and the substrate areseparated again, the substrate material begins to flow, by virtue of thehigh temperature of the substrate. As a result, surface roughnessesintroduced into the substrate are smoothed off, and that also includesthe transferred structuring effects. The structuring effects produced inthe substrate do not durably remain both in the flow temperature rangeand also in the elastic temperature range.

In FIG. 2 b the surface of the stamping roller in the region I is at atemperature within the elastic temperature range T_(elast). In theregion II the temperature is within the plastic temperature rangeT_(plast) and the region III is again within the elastic temperaturerange. When the structured surface of the stamping roller is shaped ontoa substrate, the structures are shaped in the regions I and III, but thesubstrate elastically resiliently returns to its original shape again.In the region II, a permanent surface structuring is produced in thesubstrate by the shaping operation. Thus with such a temperature profilethe result produced is a substrate 43 with a positive image, in which nosurface structurings are durably permanently impressed into thesubstrate in the regions I and III and the surface structurings aredurably permanently impressed in the region II. The substrate 43corresponds to the substrate 43 in FIG. 2 a on an enlarged scale.

FIG. 3 a shows the same portion as in FIG. 2 a, in another embodiment ofthe process. In FIG. 3 a the surface of the replication roller 41, whichcarries the diffraction stamping structure 46, is raised by an innercontrollable heat source to a temperature which is within the plastictemperature range of the substrate 43.

Due to the energy input by the laser radiation 30, additional energy isintroduced in the regions 70 so that they are at a higher temperature.If the additional energy is of such a magnitude that the heating effectcauses the regions 70 to reach a temperature which is outside of andindeed above the plastic temperature range, then only the regions of thereplication surface with diffraction stamping structures 46 which havenot been additionally exposed with radiation are transferred.

This other process implementation is again diagrammatically shown inFIG. 3 b. Here the temperature profile T of the roller in the regions Iand III is in the plastic temperature range T_(plast), whereas in theregion II the temperature is within the flow temperature rangeT_(fliess). In a shaping operation, such a process implementationproduces a substrate 43 with a negative image, which has surfacestructuring in the regions I and III, whereas in the region II thesurface profile is so-to-speak healed again. The substrate 43 is thesubstrate 43 in FIG. 3 a on an enlarged scale.

The process shown in FIG. 2 a can be used to produce positive imageswhile the process shown in FIG. 3 a can produce negative images on asubstrate.

FIG. 4 is a diagrammatic view of a portion of a cross-section through areplication apparatus 35 such as for example the replication roller 41in FIG. 1 a. The replication apparatus 35 is provided at its replicationsurface with surface structurings 36. The isotherms 32 show the heatdistribution in the replication apparatus in the region of the surfacestructuring 36. For simplification purposes, the drawing only showsthree isotherms which delimit from each other regions involvingdifferent temperatures T₁, T₂ and T₃. Also shown is a laser beam 30which is directed onto the replication surface with the surfacestructuring 36 and impinges thereon, and a diagrammatic indication ofthe absorption volume 31. FIG. 4 shows in detail an implementation ofthe process for producing regions involving different temperatures. In afirst step in the process, in the proximity of the replication surfacewith the surface structuring 36, the replication apparatus 35 is set toa first temperature T₁ by means of a controllable heat source, in theregions I, II and III shown here. In the next step in the process whichhowever can also overlap in time with the first step in the process, thereplication apparatus 35 is exposed with the laser beam 30 in the regionII. In that operation the laser beam 30 is absorbed at the replicationsurface with the surface structuring 36, in an absorption volume 31. Theenergy input in the absorption volume 31 provides that the temperatureof the absorption volume 31 increases from the temperature T₁ further toa temperature T₃. Due to heat conduction, the temperature range T₁ isdisplaced further into the replication apparatus and a heat distributionas shown in FIG. 4 is produced. Depending on the initial temperature T₁and the energy input as well as the position and the extent of the laserbeam 30, it is possible to produce a temperature profile as shown inFIG. 2 b for a positive image or a temperature profile as shown in FIG.3 b for a negative image on the replication surface.

FIGS. 5 a and b show the principle by which an individualized securityfeature can be produced by various embodiments of the process. Shown atthe left in each case as a plan view is a partial region of areplication surface such as for example from the replication roller 41of FIG. 1 a with a structured surface 2. Shown at the right as a planview is a portion 4 from a substrate after the shaping operation as forexample from the substrate 43 in FIG. 1 a.

In FIG. 5 a the k-shaped surface portion 3 of the surface 2 is at atemperature T which is within the plastic temperature range T_(plast) ofthe substrate. Outside that region the surface 2 is at a temperaturewhich is outside the plastic temperature range T_(plast). In a shapingoperation with that temperature distribution a substrate 43 is providedwith a positive image 5 whose mirror-image k-shaped surface is filledwith the impression of the surface structurings of the structuredsurface 2.

In FIG. 5 b the k-shaped surface is at a temperature T outside theplastic temperature range T_(plast) and the remaining regions of thesurface 2 are at a temperature T within the plastic temperature range.The permanent impression on the substrate 43, which results from thattemperature distribution in a shaping operation, is a negative image 6,wherein the regions which are complementary to the mirror-image k-shapedsurface are filled with the impression of the surface structurings ofthe structured surface 2.

FIG. 6 shows another portion of the replication surface of thereplication roller 41 in FIG. 1 a with a diffraction stamping structure46 which is subdivided into various partial regions. Those partialregions have been formed from a limited number of diffraction patternswhich differ in respect of spatial frequency, grating spacing, curvatureof the grating, symmetry of the grating or other parameters. Asrepresentative of the many possible options, the drawing shows partialregions with three different diffraction patterns, namely 80, 81 and 82.Each partial region 80, 81, 82 has only one respective diffractionpattern. Those different partial regions 80, 81, 82 are arranged inregularly alternating relationship. Preferably the partial regions 80,81, 82 are in the form of defined surface fields of square contour, forexample with side lengths of less than or equal to 0.3 mm. By virtue ofthe process presented herein, it is now possible, by exposure withradiation, in particular laser radiation, to activate or deactivatepartial regions 80, 81, 82 for transfer from the replication roller ontothe substrate, in order to produce a positive or a negative image in areplication operation. An image 85 produced in that way has partialregion shapings 80 a, 81 a, 82 a in respect of the partial regions 80,81, 82.

In this embodiment the partial regions 80, 81, 82 of the diffractionstamping structure 46 are selected by the heat distribution in thereplication apparatus in such a way that the image 85 has image regions86, 87, 88 which each have only one kind of diffraction patterns, thatis to say in each case they are formed only from one kind of partialregion shapings 80 a, 81 a, 82 a. When viewing the image 85, those imageregions 86, 87, 88 comprising individual separate partial regionshapings appear as full-area, homogenous image regions as are known fromconventionally produced images, with the difference that the imageregions 86, 87, 88 have particular optical properties.

In the embodiment of FIG. 7 the structure of the apparatus is similar tothat of the apparatus in FIG. 2 a. In FIG. 7 exposure of the replicationroller 41 with the laser beam 30 is effected by the exposure ofirradiation regions 71 on a second surface 60 which is arrangedinternally in concentric relationship with the roller surface carryingthe diffraction stamping structure 46. The laser beam is completely orpartially absorbed in the irradiation regions 71 and a heat input intothe replication apparatus occurs. The increase in temperature in theregions 70 on the replication surface occurs due to heat conduction fromthe inward irradiation regions 71. The shape of the irradiation regions71 which are exposed with the laser beam 30 can be produced by maskprojection processes or writing processes, similarly to the embodimentof FIG. 2 a. In this embodiment the time spacing between irradiation andshaping can be very short as the rotational angle displacement betweenthe irradiation surface 71 and the contact region of the substrate andthe replication roller 41 can be very small. In particular embodimentsthe entire laser source can be integrated in the replication roller, inparticular when using diode lasers. A feed by way of one or more opticalwaveguides is possible, as well as open beam guidance preferablyextending coaxially with respect to the replication roller 41.

1. Apparatus for producing a marking on a substrate, wherein the markingproduces a particular optical effect by having a diffractively orholographically acting surface structuring or a matt surface structuringwhich scatters incident light diffusely or directedly, comprising: areplication apparatus having a replication surface which is structuredwith a surface relief, wherein the surface relief is in the form of anegative for the surface structuring of the marking; a device forproducing radiation, preferably a laser installation, which co-operateswith the replication apparatus, by the radiation being directed onto atleast one irradiation region of the replication apparatus for producingregions of different temperatures on the replication surface forming atleast one shaping region defining the marking; and a counterpressureapparatus, wherein the substrate is arrangeable between the replicationapparatus and the counterpressure apparatus in order to shape theshaping region onto the substrate in a contact region where thereplication surface contacts the substrate, producing the surfacestructuring, and wherein the feed of the radiation for producing theshaping regions extends outside the substrate, and wherein a position ofan impingement point of the radiation on the replication surface iscontrollable by a one-dimensional or multi-dimensional movement of theradiation and or that the power density in relation to surface area ofthe radiation at the impingement point of the radiation on thereplication surface is controllable, and wherein a control sequence foractuation of the radiation-producing device is extendable over more thanone operating cycle of the replication apparatus and wherein a chance inthe selection of the shaped region is effectable by a change in thetemperature distribution on the replication surface.
 2. Apparatus as setforth in claim 1, wherein the Poynting vector of the radiation uponimpingement on the replication apparatus does not point onto the contactregion and/or that the Poynting vector of the radiation upon impingementonto the replication apparatus points onto the contact region but theradiation does not reach the substrate in the contact region. 3.Apparatus as set forth in claim 1, wherein there is provided anadditional energy source which is preferably separate from theradiation-producing device.
 4. Apparatus as set forth in claim 3,wherein the additional energy source is such that the temperature of thereplication apparatus is adjustable at least in partial regions of thereplication surface by means of the additional energy source. 5.Apparatus as set forth in claim 3, wherein the additional energy sourceis formed by a heating laser device and/or an inductive heating deviceand/or a resistance heating device and/or a device for producing heatbeams.
 6. Apparatus as set forth in claim 3, wherein the additionalenergy source is arranged within the replication apparatus.
 7. Apparatusas set forth in claim 1, wherein the replication apparatus is a stampingpunch or a stamping cylinder, in particular a rotating roller. 8.Apparatus as set forth in claim 7, wherein the rotating roller is of alength of between 500 mm and 2,500 mm and/or its periphery is between500 mm and 1,500 mm.
 9. Apparatus as set forth in claim 1, wherein thereis provided a control device for controlling the irradiation regions, inparticular a freely programmable control device, wherein it ispreferably provided that the control device is adapted for actuating theradiation-producing device.
 10. Apparatus as set forth in claim 1,wherein there is provided a cooling apparatus for cooling thereplication surface, in particular partial regions of the replicationsurface, which is preferably in the form of a blower, gas flow coolingor a cooling roller.
 11. Apparatus as set forth in claim 1, wherein theradiation is directed onto the replication surface of the replicationapparatus so that it impinges on the replication surface.
 12. Apparatusas set forth in claim 1, wherein the radiation is arranged parallel tothe substrate and/or perpendicularly to the irradiation region of thereplication apparatus.
 13. Apparatus as set forth in claim 1, whereinthe replication apparatus has an inside surface which is parallel toand/or concentric with the replication surface and the radiation isdirected onto the inside surface so that the radiation impinges on theinside surface.
 14. Apparatus as set forth in claim 13, wherein,arranged between the inside surface and the replication surface is orare a metal film, in particular a film of nickel or a nickel compound,and/or an absorption layer and/or a heat-conducting layer and/or atransparent layer, in particular a plate or a cylinder which aretransparent in relation to the wavelength of the radiation. 15.Apparatus as set forth in claim 1, wherein the radiation producingdevice has a plurality of laser sources which are spaced from each otherand which are in the form of a diode laser array and are individuallyactuatable.
 16. A process for producing a marking on a substrate,wherein the marking produces a particular optical effect by having adiffractively or holographically acting surface structuring or a mattsurface structuring for diffusely or directedly scattering incidentlight, wherein energy in the form of radiation, preferably laserradiation, from a device producing radiation is used for producingregions of different temperatures on a replication surface of areplication apparatus forming at least one shaping region defining themarking, and wherein the replication surface is structured with asurface relief, wherein the surface relief is in the form of a negativefor the surface structuring of the marking, and wherein the surfacerelief of the replication surface is shaped onto the substrate, formingthe surface structuring, by the replication apparatus contacting thesubstrate under pressure, and wherein the radiation for producing theshaping regions is fed outside the substrate, and wherein a position ofan impingement point of the radiation on the replication surface iscontrollable by a one-dimensional or multi-dimensional movement of theradiation and/or that the power density in relation to surface area ofthe radiation at the impingement point of the radiation on thereplication surface is controllable, and wherein a control sequence foractuation of the radiation-producing device extends over more than oneoperating cycle of the replication apparatus, and wherein a change inthe selection of the shaped region is effected by a change in thetemperature distribution on the replication surface.
 17. A process asset forth in claim 16, wherein the replication apparatus is subjected toa temperature control effect at least in partial regions of thereplication surface using an additional energy source which ispreferably separate from the radiation-producing device.
 18. A processas set forth in claim 17, wherein at least one heat combination regionis formed on the replication surface by an energy input from theadditional energy source and an energy input from theradiation-producing device.
 19. A process as set forth in claim 17,wherein the shaping region is shaped, which corresponds to the heatcombination region or which is complementary to the heat combinationregion.
 20. A process as set forth in claim 17, wherein the temperatureof the replication surface, which prevails during the shaping operation,is set to a plastic temperature range in at least one region outside theheat combination region by the temperature control effect operation, andthat the temperature of the replication surface, which prevails duringthe shaping operation, is set to a flow temperature range in at leastone region within the heat combination regions by the energyadditionally introduced with the radiation.
 21. A process as set forthin claim 20, wherein a range within +/−2% of a substrate-specificplastic temperature is used as the plastic temperature range.
 22. Aprocess as set forth in claim 19, wherein the range of 180° C. +/−2.5°C. is used as the plastic temperature range.
 23. A process as set forthin claim 17, wherein the temperature of the replication surface, whichprevails during the shaping operation, is set to an elastic temperaturerange in at least one region outside the heat combination region by thetemperature control effect operation, and that the temperature of thereplication surface, which prevails during the shaping operation, is setto a plastic temperature range in the region within the heat combinationregions by the energy additionally introduced with the radiation.
 24. Aprocess as set forth in claim 23, wherein a range within +/−2% of asubstrate-specific plastic temperature is used as the plastictemperature range.
 25. A process as set forth in claim 23, wherein therange of 180° C. +/−2.5° C. is used as the plastic temperature range.26. A process as set forth in claim 16, wherein the replication surfaceis subjected to a homogenous temperature control effect completely or insurface portions prior to the energy input from the radiation-producingdevice.
 27. A process as set forth in claim 16, wherein the temperatureof the replication surface is set to at least 100° C., preferably atleast 170° C.
 28. A process as set forth in claim 16, wherein thetemperature control of the replication surface is effected by electricalheating and/or by pre-heating radiation, in particular a pre-heatinglaser beam.
 29. A process as set forth in claim 16, wherein thereplication surface is cooled completely in partial regions after theshaping operation and/or prior to a following energy input from theradiation-producing device.
 30. A process as set forth in claim 16,wherein the radiation is directed onto the replication surface of thereplication apparatus and/or that the radiation is introduced onto asurface remote from the replication surface.
 31. A process as set forthin claim 16, wherein the radiation is introduced into the replicationapparatus before and/or while the heat combination region resultingtherefrom is in contact with the substrate.
 32. A process as set forthin claim 16, wherein a replication roller is used as replicationapparatus and that the introduction of radiation into the replicationroller is effected at a first angular position of the replication rollerand the contact of the replication roller with the substrate is effectedat a second angular position of the replication roller, wherein anintermediate angle which is different from 0°, preferably less than180°, in particular less than 90°, is set between the first angularposition and the second angular position in the direction of rotation ofthe replication roller.
 33. A process as set forth in claim 16, whereinthe radiation acts on the replication apparatus over an area and/or inpoint form sequentially.
 34. A process as set forth in claim 16, whereinthe radiation-producing device has a plurality of laser sources whichare preferably spaced from each other and which in particular are in theform of a diode laser array and in particular are individuallyactuatable.
 35. A process as set forth in claim 16, wherein the controlsequence extends over more than a revolution of the replication rolleror a stroke of the stamping punch.
 36. A process as set forth in claim16, wherein the energy input from the radiation-producing device isintroduced in the heat combination region by direct absorption and/orheat conduction.
 37. A process as set forth in claim 16, wherein anapparatus as set forth in claim 1 is used.
 38. A method for forming alight scattering marking on a substrate comprising the steps of:irradiating a region of a replication surface with laser energy, wherebysaid irradiated region has a temperature greater than a non-irradiatedregion of said replication surface, at least one of said irradiatedregion and said non-irradiated region having a stamping structure;pressing said replication surface on the substrate whereby said stampingstructure thermally deforms the substrate to form the light scatteringmarking, wherein the marking has boundaries defined by said irradiatedand non-irradiated regions of said replication surface.